Re: [PATCH 02/17] midx: split `get_midx_checksum()` by adding `get_midx_hash()`

> When trying to print out, say, the hexadecimal representation of a
> MIDX's hash, our code will do something like:
> 
>     hash_to_hex_algop(get_midx_checksum(m),
>                       m->source->odb->repo->hash_algo);
> 
> , which is both cumbersome and repetitive. In fact, all but a handful of
> callers to `get_midx_checksum()` do exactly the above. Reduce the
> repetitive nature of calling `get_midx_checksum()` by having it return a
> pointer into a static buffer containing the above result.
> 
> For the handful of callers that do need to compare the raw bytes and
> don't want to deal with an encoded copy (e.g., because they are passing
> it to hasheq() or similar), introduce `get_midx_hash()` which returns
> the raw bytes.

> diff --git a/midx.h b/midx.h
> index 7c7e0b59121..e188ffeb578 100644
> --- a/midx.h
> +++ b/midx.h
> @@ -85,7 +85,8 @@ struct multi_pack_index {
>  #define MIDX_EXT_BITMAP "bitmap"
>  #define MIDX_EXT_MIDX "midx"
>  
> -const unsigned char *get_midx_checksum(const struct multi_pack_index *m);
> +const char *get_midx_checksum(const struct multi_pack_index *m) /* static buffer */;
> +const unsigned char *get_midx_hash(const struct multi_pack_index *m);
>  void get_midx_filename(struct odb_source *source, struct strbuf *out);
>  void get_midx_filename_ext(struct odb_source *source, struct strbuf *out,
>  			   const unsigned char *hash, const char *ext);